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the only way to know if your ductwork is OK is to measure it's dimensions, lay out all the fittings on paper, and evaluate the layout for CFM, Distribution and air Speed. also, the ductwork needs to be in the correct position, and the proper registers for throw and distribution in the rooms. was a blower door test done on the ductwork for leakage? if not, then it's doubtful the ductwork is "OK"...

in the 80's it was rare to seal any fittings to the plenum, and rare to seal the take offs to the registers.
here's a test for you.
pull any register off the wall, and look into the duct. is there any sealant on the ductwork? if not your ductwork is inadequate for your house by today's standards of energy efficiency, unless ALL your ductwork is inside the house. nothing in the attic, nothing in the crawlspace.

The contractors (the two I'm considering) have been in my attic. The others didn't go up there and weren't invited back after they tried to "sell" me anyway. The two contractors have seen the sizing and layout of the ducts and verified the positioning of the registers. The FPL energy survey included a blower door test. Ducts had already been sealed at the plenum (current A/C is not original 80s equipment and neither is the ductwork). The only leaks detected were where the ducts meet the boots at the registers. There is sealant in the ductwork at the registers now because I stood there and watched while those repairs were made last week.

Are your room temperatures relatively even of do you have a room or tow that's always too hot/cold? If temps are even the ductwork is at least on the right track. Also smaller equipment doesn't require as much ductwork. Your single 20x20 is too small for a 3.5ton, but would be fine for a 2 ton. If you go up in A/C size bigger ductwork is normally required.

Remember, the sales guy has a lot to consider, and may have limited knowledge. In the unlikely event he knows enough to recommend $x thousand for duct repair/replacement, it might well lose him the job when the next guy assures you 'nah, ya don need all that.'.

Did you pay for his time? No? Then do you think there my be conflict of interest? He doesn't get paid for NOT making the sale.

Install 2 stage. Divide the incremental cost over 180 months, then subtract the energy savings, you'll feel pretty foolish not spending the extra few pennies (which may not be extra if price of electricity jumps).

Also, If high only happens 20% of the time, you are only running 'emergency brake engaged' 20% of the time. Sounds like current duct is likely more than sufficient for low stage, which will be where you run mostly. Adding a return will probably loosen the brake some for high and ensure its full off for low.

There are perfect solutions and near perfect solutions. At some point, unless you are NASA, the cost and benefit of going from near perfect to perfect simply don't match up.

Are your room temperatures relatively even of do you have a room or tow that's always too hot/cold? If temps are even the ductwork is at least on the right track. Also smaller equipment doesn't require as much ductwork. Your single 20x20 is too small for a 3.5ton, but would be fine for a 2 ton. If you go up in A/C size bigger ductwork is normally required.

Keep in mind my existing Rheem air handler is a 4 ton, single speed. Air flow feels good to me at all of the registers, even though the small return is sucking the air filter for all it's worth. The only hot spot was the 10x15 space in the NE corner that I use as an office. It was originally a screen room, later enclosed as conditioned space. During insulation upgrade last week, I discovered the previous owner had failed (or forgotten) to insulate the attic above that space. Since I now have R30 up there, the temp in that space is the same as other rooms. It's 3:30 in the afternoon and I'm in the office and comfortable at 77 degrees and 39% RH.

Remember, the sales guy has a lot to consider, and may have limited knowledge. In the unlikely event he knows enough to recommend $x thousand for duct repair/replacement, it might well lose him the job when the next guy assures you 'nah, ya don need all that.'.

Did you pay for his time? No? Then do you think there my be conflict of interest? He doesn't get paid for NOT making the sale.

Install 2 stage. Divide the incremental cost over 180 months, then subtract the energy savings, you'll feel pretty foolish not spending the extra few pennies (which may not be extra if price of electricity jumps).

Also, If high only happens 20% of the time, you are only running 'emergency brake engaged' 20% of the time. Sounds like current duct is likely more than sufficient for low stage, which will be where you run mostly. Adding a return will probably loosen the brake some for high and ensure its full off for low.

There are perfect solutions and near perfect solutions. At some point, unless you are NASA, the cost and benefit of going from near perfect to perfect simply don't match up.

As I've tried to say a couple of time, the "sales guys" were discounted from the get go... shown the door and not invited back. The two contractors who quoted me on the Trane XL20i and the XB14 happen to be Trane certified comfort specialists AND they are the "owners" of their own A/C companies that have been in business in my area a long time... one since 1975, the other since 1985. They're not "sales guys" IMHO and each spent several hours in my home checking things and going over details with me. As I've said before, neither is trying to sell me on any one choice over the other.... it's all up to me.

I've gotta say, at this point, I may be better off waiting at least until December to see how the repairs to my 3.5 ton Rheem system impact my electric bill. Of course, I'll continue my analysis of options and may or may not decide to move on the current Trane rebate offering before it expires.

I tried to post a reply, but I think I messed up and hit "Reply to Thread" instead of "Reply With Quote". Since I'm a guest, not a pro, I think that post went to the round file.

Anyway, my response to your recommendations is this:

I had FPL out last week to do the energy survey. They checked for duct leaks, window/door leaks, and evaluated my insulation. As a result, I had the ducts sealed and added R30 to bring the total to R38. Doors and windows were tight, so no repairs were required. This information was provided to the contractors bidding on my A/C replacement and all but one came up with 3.5 ton single stage or 4 ton two stage as recommended solutions. The one lone wolf said I was stuck with 3.5 ton single stage because anything else would be over or under-sized, so I shouldn't even look at a two stage option. BTW, he was a Carrier dealer and offered me only one solution. Turns out the p/n suite he offered me as "Performance Series" is listed on Carrier's website as a "Comfort Series" p/n. Guess he thought I wouldn't check!

FYI, the Carrier guy was a "sales guy". I could tell by what he did or didn't discuss with me. Besides that, the title on his business card was "Replacement Manager" and he sat in his truck doing his calculations, which he automatically assumed I wouldn't or shouldn't need to know.

As far as it being "easier to set up," that is not something that really concerns you, this is for the contractor to handle. Find out some info on the T-stat that will go with the XL20i, make sure you are going to be okay with it.

I wasn't concerned with my interaction with a complicated t-stat.... I've been pretty much of a geek since I was introduced to a computer at my first job working for the DoD in 1966, before most folks even knew that electronic calculators existed! I was more concerned with the tech doing the install setting all the switches properly for my setup. I've been all over the web reading about install issues where the tech forgot something and the callback tech couldn't find it, so it took months of frustration for the homeowner to get it resolved.

Originally Posted by S.T.Ranger

The last thing I would recommend is a ten year labor warranty (Trane already offers a 10 year on parts when registered, 12 year on compressor for the XL, as well as two year labor with the XL). When averaged, the annual cost is minimal. This will insure that for ten years repair costs are limited to the annual average of the labor warranty.

Good luck with your decision, Florida Joy.

Yep, I've decided to take the 10 year extended warranty. It took me awhile to convince myself it was worth it, given that I'll continue paying my home warranty annual premium and could save myself a few bucks a year and still get labor, if required, and only have to pay my deductible. But in the end, I've decided it's worth it to be sure any labor for warranted parts replacement is performed by a Trane trained tech, instead of whoever's next on the contractor rotation used by my home warranty company.

How old is the duct system you have at present? Did you just pay to have the sealed?

I don't know for sure, but the FPL rep that did the energy survey and blower door test said it looked like they were NOT the 1980 original ducts. Since the replacement. A/C is dated 12/99 and the screen room enclosure was done around the same timeframe, I'm guessing the ductwork may have been replaced/upgraded when the current A/C was installed. Yes, I just paid to have the ductwork tested and sealed.

Have you had an efficiency test done on your existing system? How many BTU's is it actually putting out? Are the coils clean? Since you are this deep into it you may want to consider hiring an air balancing company? (Don't freak out everyone) just to get them out to the site and actually measure the cfm's leaving the supply registers. Add them up. You want them to use a FLOW HOOD. It's not expensive at all. You can even rent them yourself. Let's see what you are actually starting with, rather than just replacing equipment. You need to make what you have as efficient as it can be......a new box is not the first answer.

The return may me too small, can you add one in the master bedroom? (I understand you just have one return?)

Have you had an efficiency test done on your existing system? How many BTU's is it actually putting out? Are the coils clean? Since you are this deep into it you may want to consider hiring an air balancing company? (Don't freak out everyone) just to get them out to the site and actually measure the cfm's leaving the supply registers. Add them up. You want them to use a FLOW HOOD. It's not expensive at all. You can even rent them yourself. Let's see what you are actually starting with, rather than just replacing equipment. You need to make what you have as efficient as it can be......a new box is not the first answer.

The return may me too small, can you add one in the master bedroom? (I understand you just have one return?)

My reasons for considering equipment replacement at this time are:

(1) The system is at least 12 years old (mfg date 12/99) and approaching end of life. I've had 3 different issues repaired inside the condenser housing over the past 3 years. Only a matter of time before something fails again.

(2) The bottom of my condenser housing has rusted through, causing the compressor to fall over onto the accumulator. My home warranty covered those repairs last week and I'm up and running, comfortably, right now. It's only a matter of time before something else fails.

(3) The condenser housing was installed half on/half off a cement slab less than 2 inches from a sprinkler head, so the coil fins are so corroded I'm afraid to hit them with the water hose. It's only a matter of time before that causes another failure.

(4) When the unit was running before the recent accumulator failure, my electric bill was too high. For example, my monthly bill in the summer months was running 4 or 5 times the amount I pay monthly in the spring and fall. Could have been caused by the leaky accumulator... maybe the bill will go down now.

Yes, the return is way too small. Yes, I need to add a return. The air handler sits on a fabricated stand in the corner of my laundry room, which backs up to the entry hall on one side and the hallway to two of the bedrooms on the other side. I Now have one 20x20 filtered return at that corner in the b/r hallway that feeds the air handler from underneath, and I can add another at that corner in the entry hallway to feed through the same space under the air handler. This is the return solution proposed by the contractors I'm working with.

you may want to consider hiring an air balancing company? (Don't freak out everyone) just to get them out to the site and actually measure the cfm's leaving the supply registers. Add them up. You want them to use a FLOW HOOD. It's not expensive at all. You can even rent them yourself.

Curious.... wasn't this part of the "duct test" I just paid my utility company to do as part of their "energy survey"? They hooked up a door boot and suction fan to my front door and then went around to each register one by one with a hood fitted with tubing running to a meter, blocking each register and taking readings with the meter. The resulting readings for each register indicated how much airflow was being lost in each room due to ductwork leakage. I had the identified leaks repaired last week.

that test can point out leakages to the exterior of the home, but it can also hide some.
another test is called the same thing, but the blower door it connects to is the one on your air handler. using a product called a duct blaster. it ramps up pressure on your sealed ducts, and the computer spits out a percentage of leakage. I shoot for zero... old ducts I have sealed, I accept 6% new stuff with new equipment gets down in the 3% range.
anyway, to answer your questions, the air balancing company will determine how air is distributed in each room. and that along with your floorplan should help you balance what should be in each room to what is actually in each room.

The TRUE highest cost system is the system not installed properly...
The three big summer hearththrobs...
Mel Gibson
Dwane Johnson
The A/C repairman